A 76-year-old Hispanic woman with no significant past medical history presented with an asymptomatic, slowly enlarging lesion in the right preauricular area (see the accompanying figure). She had first noted the lesion one year earlier. Physical examination revealed a 7 × 6 cm irregular plaque with varied pigment and rolled pearly borders. No cervical lymphadenopathy was present, and the remainder of the cutaneous examination was unremarkable.
The answer is B: pigmented basal cell carcinoma. Punch biopsy of the lesion revealed a pigmented basal cell carcinoma. The tumor, which was found to infiltrate to the muscle, was successfully surgically excised.
The most common subtype of melanoma, superficial spreading melanoma, may exhibit the “ABCDs” of melanoma. These include asymmetry, border irregularity, color variegation and diameter greater than 6 mm. However, the rolled borders and pearly quality of the lesion are not typical of melanoma.
Seborrheic keratoses are benign lesions that can exhibit varied pigmentation. However, they are typically brown, waxy, “stuck-on” plaques with an irregular, cobblestone-like surface.
Venous lakes are vascular lesions that typically occur on the lips or ears. Clinically, they may be dark purple or even black and thus mimic pigmented lesions. However, they do not reach the large size or exhibit the irregular pigment seen in this lesion.
Skin tags are usually located in intertriginous areas such as the axillae or neck. They are typically small, flesh-colored to tan pedunculated papules, although they will occasionally undergo a color change if they become thrombosed or necrotic.
Nonmelanoma skin cancers are by far the most common type of cancer in the United States, with an incidence similar to that of all noncutaneous malignancies combined.1 Approximately 80 percent of nonmelanoma skin cancers are basal cell carcinomas.
Basal cell carcinoma has several clinical variants. Nodular basal cell carcinoma may be recognized by its typical clinical appearance of a pearly nodule, often with a central depression or erosion, and rolled, telangiectatic borders. Pigmented basal cell carcinoma is a less common variant. This type has been reported to be more frequent in black and Hispanic populations in North America.2 Histologically, most pigmented basal cell carcinomas exhibit a nodular pattern with a varied distribution of melanin pigment.3 Clinically, this correlates to the example seen in this patient, of a pearly, irregular plaque with rolled borders and an irregular distribution of melanin pigment. While these clinical characteristics are often helpful, the correct diagnosis requires biopsy for histopathologic examination. The main disorder to exclude in the differential diagnosis of such a lesion is that of malignant melanoma.